The present invention relates to a polling period controlling apparatus and particularly to a polling period controlling apparatus for use in network management.
In an office, a factory, a university, or any other facility, a network is provided in which work stations, personal computers (referred to as PCs hereinafter), printers, routers, and other equipment are connected with each other, as shown in FIG. 8, and used for such as communication and data transfer. FIG. 8 illustrates a network where a work station 52, a group of first to nth PCs 53, 54, . . . , 55, and a printer 56 are connected via a LAN 51 to each other. The LAN 51 may further be connected to another network via a router 57.
In such a network, network management is carried out for monitoring various forms of management information in real-time including the usage of central processing units (CPU) in the PCs 53 to 55 and the number of prints on the printer 56. It is assumed that the network management is conducted by the work station 52 which may thus be called a managing unit (thus being referred to as a managing unit 52 hereinafter). Accordingly, the PCs 53 to 55 and the printer 56 connected via the LAN 51 are called managed units.
For carrying out a network management, the managing unit 52 sends a polling packet to the managed units which in turn read out corresponding management information values from their storages 53a to 55a and send them in the form of polling response packets back to the managing unit 52.
It is necessary for the polling to dynamically determine its polling period for reading out the management information values from the managed unit and monitoring their temporal variation in real-time. A couple of methods for dynamically determining the polling period are known as described below. The first method is based on a round trip time from the sending a polling packet to the managed unit to the receiving a polling response packet by the managing unit. The second method is based on the number of the managed units being in operation, described later in detail.
More particularly, the first method involves a technique of shortening the polling period when the round trip time from the sending a polling packet to the managed unit to the receiving of a polling response packet by the managing unit is comparatively long, i.e. it is predicted that the polling and polling response packet traffic on the network becomes heavy, or lengthening the polling period when the round trip time is short, i.e. it is predicted that the traffic becomes not heavy. The second method is a technique of determining the polling period by assigning a bandwidth for polling in network management (thus being referred to as the network management bandwidth hereinafter) to all the managed units equally so that the traffic of the polling packets can be limited to less than the management bandwidth.
However, the first method determines the next polling period without concerning a temporal variation of the management information values of a managed unit and thus hardly enables to trace temporal variations of the management information values. It is now assumed that the managing unit 52 requires to receive a management information values from the printer 56 and determines the polling period from the time of receiving the polling response packet responsive to the polling packet. The polling period is determined regardless of temporal variations of the number of prints on the printer 56 and, when the number of prints is largely varied with time, has to be lengthened and fails to trace temporal variations of the management information values.
The second method permits the managing unit to poll all the managed units with the same polling period even if the management data in one managed unit is moderately varied with time while that of another managed unit is sharply varied with time, thus failing to trace temporal variations of the management information values.
It is an object of the present invention to provide a polling period controlling apparatus capable of polling with a period which can trace temporal variations of management information values in a managed unit and particularly, a polling period controlling apparatus capable of polling with a proper period which gives no excessive load to the network.
To accomplish the above object, the present invention is characterized in that a polling period controlling apparatus for use in network management comprises a first means for calculating a close-to-maximum frequency, including the maximum, from a sequence of management information values received from a managed unit and extracting a period from the calculated frequency, in which the period extracted (referred to as an extracted period hereinafter) is determined as the next polling period.
Secondly, the present invention is characterized in that the polling period controlling apparatus further comprises a second means for calculating a bandwidth required for polling with the extracted period (referred to as a required bandwidth hereinafter) and a third means for comparing the required bandwidth with a predetermined network management bandwidth for the network management, in which the extracted period is determined as the next polling period when the required bandwidth is smaller than the network management bandwidth.
Thirdly, the present invention is characterized in that the period from the network management bandwidth is determined as the next polling period when the required bandwidth is greater than the network management bandwidth.
According to the first feature, the period extracted according to the exactly or a close to maximum frequency of a sequence of the management information values obtained from a target managed unit is determined as the next polling period to be used, hence allowing the management information values to be obtained through tracing their temporal variations from the managed unit.
According to the second or third feature, the management information values can be obtained through tracing their temporal variations from a target managed unit. Also, it will be avoided that the traffic of polling packets and polling response packets for monitoring management information values may give a heavy load to the network.